The present invention relates generally to magnetic recording systems and more particularly to initialization of magnetoresistive read transducers during fabrication and assembly of such recording systems.
Magnetic disk drives are information storage devices which store information by magnetically recording data on magnetic storage media. A magnetic disk drive typically utilizes one or more rotatable disk media having concentric data tracks formed on one or both surfaces of each disk containing the recorded information, a transducer for reading data from or writing data to the various data tracks and a head positioning actuator connected to the head or heads for moving them to the desired data track and maintaining it over the track centerline during read or write operations. The head is attached to or formed on a surface of an air bearing slider which is supported adjacent the data surface of the disk media by a cushion of air generated by the rotating disk. The slider is connected to a support arm of the head positioning actuator by means of a suspension assembly.
The use of magnetoresistive (MR) sensors to sense or read magnetically recorded data is well-known in the art. It is also well-known that both longitudinal and transverse magnetic bias fields must be provided in the MR sensing element to eliminate Barkhausen noise and to maintain the MR sensor in its most linear operating range. Commonly assigned U.S. Pat. Nos. 4,024,489; 5,079,035; 3,840,898 and 4,103,315 discuss and disclose MR sensors in which various bias schemes utilizing both hard or soft magnetic materials and/or exchange coupling to provide the transverse and longitudinal bias fields required in the MR element. For example, U.S. Pat. No. 5,079,035 discloses an MR sensor in which a ferromagnetic MR element extends over only a central active region of the sensor. A layer of hard magnetic material is provided in each of the sensor end regions forming an abutting junction with the ends of the MR element to provide a longitudinal magnetic bias field in the plane of the sensor parallel to the surface of the magnetic media disk. The sensor's central active region includes the MR element, a non-magnetic spacer layer and a soft magnetic layer which provides the transverse magnetic bias field for the MR element.
The magnetic transducer is manufactured utilizing thin film deposition techniques and generally includes an MR read sensor in combination with an inductive write transducer to provide both recording and reproducing of data. The magnetic transducers are fabricated in a batch process on a wafer which is then cut or diced into individual sliders with the transducer formed on an end surface thereof. The dicing process may also include additional batch processing at the row level to form the air bearing surface for the slider. When the fabrication of the individual sliders is complete, each slider is then attached to a suspension assembly and the suspension assembly is attached to a support arm of a head actuator assembly with the heads typically arranged in a vertical configuration referred to as a head stack or actuator head stack.
The completed actuator assembly is subsequently assembled with other components such as the magnetic media disks to form a magnetic disk drive. At some point during the fabrication/assembly process the MR sensor must be initialized by impressing a magnetic field across the MR sensor in a preferred direction, typically parallel to its longitudinal axis and the plane of the magnetic media disk. Subsequent to this initialization process, the MR sensors may be subjected to various stresses resulting from handling during the manufacturing and assembly process described above. These stresses tend to degrade the magnetic performance of the MR heads. For such degraded heads, re-initialization of the MR head after such handling is known to recover the head in most instances; i.e., to return the head to its proper magnetic state. Conventional MR head and disk drive designs typically mount the sliders in pairs such that the MR heads on opposing sides of the magnetic disk media have opposing initialization directions. For this reason, and because of limitations on practical magnet designs, an MR head in a actuator assembly cannot be re-initialized without "reverse" initializing its neighboring heads. Thus, handling damage incurred subsequent to actuator assembly is left untreated resulting in degraded performance and even disk drive failure.